Spread the oatmeal in a single layer and bake for 8-10 minutes or until lightly browned. Cool.
Line 2 cookie sheets with parchment paper or silipats. In a large bowl, cream together the butter, vanilla, and sugar. Add the egg, beat until fluffy.
Add the flour, baking powder, mace, salt, and oatmeal. Mix until well combined.
Fold in butterscotch chips. Place tablespoon-sized blobs of dough on the lined cookie sheet about 1/2 inch apart and bake for 12-14 minutes or until they look just "set" and the bottoms are just golden. Don't overbake! The center may still be slightly soft.
Carefully remove the cookies still on the parchment or silipats to a wire rack to cool completely.